When I purchased my K&N Air Intake, it seems that I only get 12 MPG around the city now. Is this right?? Aren`t I supposed to get better gas mileage?

The only mods I have on my car is a, MagnaFlow Exhaust System and a K&N Air Intake.

This is for my 02 Z28.
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2002 Camaro Z28 35th Anniversary. Blue Metallic. 17,900 Miles (Sold) :'(
1997 6spd Toyota Supra
Boost Logic T67 single turbo, 1000cc fuel injectors, AEM EMS, TEIN Flex coilovers, Titan sways